Talk:Neo 1973 GTA01 Power Management

From Openmoko

The SPI connected LCM asic (JBT6K74-AS(PI)) doesn't do any kind of drawing. It mainly controls the power states and the format in which data is shifted out to the LCD (timing), but also includes gamma correction and there are two unexplained parts called "built-in oscillator" and "booster".

Built in oscillator and booster probably together provide the required voltages to supply the LCD, which will typically require at least one supply other than 3.3V.
--Speedevil 01:27, 26 July 2007 (CEST)

5V supply

I need a 5V supply for this and this - total power draw should be 730 mW (max).
Some advice (best practice) would be appreciated on where to do this and how?Johan 19:24, 25 July 2007 (CEST)

You've misread the maxim parts datasheet.

Maximum power is an absolute maximum rating, it's not a normal operating condition.

You have to really abuse it to get it to dissipate that much power - for example supplying lots of current into the input pins trying to take them beyond the supply rails.
The actual power draw is low single digit milliamps at 5V, maybe 25mW or so when active.

I would suggest that rather than the complex sensor conditioner, you simply use a 3.3V ADC.

OK - thats good news. We still need 5V for the transducer though don't we?

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The SPI connected LCM asic (JBT6K74-AS(PI)) doesn't do any kind of drawing. It mainly controls the power states and the format in which data is shifted out to the LCD (timing), but also includes gamma correction and there are two unexplained parts called "built-in oscillator" and "booster".

Built in oscillator and booster probably together provide the required voltages to supply the LCD, which will typically require at least one supply other than 3.3V.
--Speedevil 01:27, 26 July 2007 (CEST)

5V supply

I need a 5V supply for this and this - total power draw should be 730 mW (max).
Some advice (best practice) would be appreciated on where to do this and how?Johan 19:24, 25 July 2007 (CEST)

You've misread the maxim parts datasheet.

Maximum power is an absolute maximum rating, it's not a normal operating condition.

You have to really abuse it to get it to dissipate that much power - for example supplying lots of current into the input pins trying to take them beyond the supply rails.
The actual power draw is low single digit milliamps at 5V, maybe 25mW or so when active.

I would suggest that rather than the complex sensor conditioner, you simply use a 3.3V ADC.

OK - thats good news. We still need 5V for the transducer though don't we?